Palladium-silver-platinum alloys



Sept. 13, 1938. E. M. WISE FALLADIUM-SILVER-PALATINUM ALLOYS Filed Dec. 15, 1954 d @A 0A MA HIAAWAMa @AAA/@wwwa V um? M/A. MNA ,.V V *Am AXA Moa NVMMMNAMMWMX AAAAA/ AA l WMWWMWMAAAW www@ m XMAWWMAAAM, WJYNAH WW ,AM www A wv A@ ^../M\ 6 W V WANNA AM A M J/ www M A @WMA Awww WM A AWAAAA MA AV 0/ NAMAAMAAAAMWAA AA. MMM N A ,A AAA Mw MAMA AAAA M AAAAA MA w AAA AMM N m 0 NWMVA MMM /M AAMM5 A W MAH m NAAAAAAM A A VMM MMAAAAAMAA Awww A A M a @WWA WWMAMMAA` 7 AWM www o0 .//MVWW w MNHN INVENTORZ e; Wy Mm d Mm ATTORNEYS 15 the setting of diamonds and the like.

Patented Sept. 13, 1938 PATENT OFFICE PALLADIUM- SILVER-PLATIN UM ALLOYS Edmund M. Wise, Westfield, N. J., assignor to The International Nickel Company,` Inc., New York, N. Y., a corporation of Delaware ApplicationDecember 15, 1934, Serial No. 757,623

Claims.'

'I'he present invention relates to alloys of palladium, platinum .and silver and more particularly to a noble white alloy containing palladium, platinum and silver, substantially resistant to 5 -nitric acid.`

Heretofore, high grade jewelry has been made from either carat gold alloys, o r from alloys consisting almost wholly of platinum or palladium hardened by the addition of small amounts of iridium, ruthenium, or the like. It has been known that, due to its color, tarnish and corrosion y resistanceand other chemical and physical properties, platinum has been' peculiarly well adapted for use in the productiony of jewelry, such as in Platinum, however, has been a yrare and expensive metal, and in general the cost of platinum metal jewelry was prohibitive for large articles of jewelry and very much in excess of that of carat gold alloys, such as 12 to 14 kt. gold. Many attempts have been made to produce a precious white alloy suitable for jewelry and other purposes where high V stability and moderate cost are essential. Thus, various types of White gold alloys were proposed in which gold was present as a major constituent.

Attempts have also been made to use commercially pure palladium, palladium and silver, platinum and silver, etc. These white metal alloys, however, involved certain shortcomings including a deficiency in tarnish and corrosion resistance, es-

pecially when exposed to the action of nitric acid, lack of ductility, strength or resistance to wear,

a tendency to fire crack on annealing, and in many cases insuicient cheapness. To be satis- A factory for jewelry purposes, an alloy must not only be readily workable,- adequately hard and tarnish resistant, but must also be resistant to nitric acid. Thus, a mode of testing which is used by jewelers for testing alloys is conducted as follows: A dropfof concentrated nitric acid is applied to the clean surface of the alloy and is allowed to remain upon Athe surface of the sample for a fewv minutes, during` which time the behavior and appearance of the drop are observed. The drop is then washed off and the condition of the underlyingmetal is noted. The metal is considered satisfactory when neither the drop itself, nor the surface of the metal are appreciably discolored during the test. It is known that the usual white gold alloys are not completely resistant to the aforementioned nitric acid test. For instance, 14 kt. white goldA alloys became discolored during the test'. The staining became more intense in 12 and 10 kt. white golds, and in alloys with a lower gold content than 10 kt. alloys (Cl. 'l5-172) the attack was usually very vigorous4 and the drop of nitric acid turned green. It is also known thatv commercially pure palladium, alloys of palladium and nickel, and alloys of palladium and silver do not withstand successfully the nitric 5 acid test and have therefore been unsuited for use in the jewelry art. Likewise, platinum silver alloys were not useful for jewelry, as they were extremely diilicult to cast and to work when the platinum content was higher than about 40%, 10 and they were not resistant totarnish and to nitric acid when the platinum content was less than about 40%. Although many proposals have been made by those skilled in the art to provide the trade and the public with precious alloys, 15

especially white alloys, having the requisite resistance to tarnish and nitric acid, workability and moderate cost, none as far as we are aware has been wholly satisfactory and successful in practical, commercial and industrial use. 20

I have discovered that the addition of relatively small percentages of platinum to certain special palladium silver alloys renders such alloys not only readily workable, but also resistant to tarnish and to nitric acid. 25

It is an object of the present invention to provide an alloy containing palladium, platinum and silver which is strong, adequately hard and readily workable, and which possesses adequate resistance to tarnish, to corrosion and to nitric acid. 30

It is another object of the invention to provide a noble white alloy containing palladium, platinum and silver, which is relatively inexpensive,

and which can be cast and fabricated easily and economically. 35

A further object 'of the invention is to provide a palladium-platinum-silver white `alloy which possesses the appearance, quality and the properties thatmake it desirable for use in the production of jewelry and other purposes where high 40 stability and moderate cost are required.

It is also within the contemplation of the present invention to provide a noble white alloy of palladium, platinum and silver which is suitable 45 for jewelry and similar purposes, and which contains substantially no gold, thereby offering an effective means for conserving gold and releasing it for essential monetary purposes. i

The invention further contemplates the provi- 50 sion of a. white alloy containing palladium, platinum and silver suitable for jewelry and similar purposes, whichv can be made on an industrial scale, which can be handled, fabricated and worked with conventional appliances and equip- 55 ment, and which is relatively cheap and permits wide use.

Other objects and advantages of the invention will become apparent from the following descrip.

tion taken in conjunction with the accompanying drawing showing a ternary diagram in which the alloys contemplated by the present invention are plotted on the basis of weight percentages.

Generally speaking, the present invention contemplates providing a precious white alloy containing palladium, platinum and silver in which` the palladium content `may vary from about 15% to about 82% and is preferably not less than about 60% of the platinum content of the alloy. When such conditions are observedf` the alloys of palladium, platinum and silver contemplated by the present invention possess excellent qualities in regard to color, strength, toughness, workability, resistance to wear, corrosion and nitric acid, etc., and are fully suitable for the production of jewelry and similar purposes. 1n addition, the alloys are not only less expensive than corresponding known white gold alloys but are also so superior to them in several respects, such as resistance to nitric acid, workability etc., as to be preferable to the -gold alloy for jewelry and yother uses where high stability and moderate cost are desirable.

Of course, the composition of the alloy permits of wide variations and a wide range of physical and chemical properties may be obtained by properly varying the proportion of the ingredients of the alloy and especially by controlling the ratio of the palladium to platinum content thereof.

In general, the tarnish'and nitric acid resistance of the new alloy improves with increases in the combined content of palladium plus platinum in the alloy. When the palladium content is not less than about 60% of the platinum content, the nobility ofthe alloy varies with the combined palladium plus platinum content in'a manner analogous to that of commercial gold alloys, and is equal or superior to that of a corresponding white gold alloy, or an alloy having a gold content approximately equal in weight to the' combined palladium plus platinum content of the new alloy. For instance, the palladium-silver-'platinum al` loys containing more than of palladium attain a resistance to nitric acid equalto that of a corresponding white gold alloy when 5% or more of platinum is present. Likewise, palladium-silver-platinum alloys containing between 15% and 35% palladium exhibit a similar resistance to l nitric acid when the combined palladium plus platinum content 'of the alloy is 40% or more.

Referring more particularly to the drawing, the most useful alloys of the palladium-silver-platinum system exhibiting a resistanceto nitric acid equal or lsuperior to that of a corresponding white gold alloy are shown'in the area A-D-G-K- The composition of the alloys expressed in weight percentages'may vary from about 15% rto about 82% palladium, from about 13% to about 60% silver, and from about 5% to about 54% platinum.

The new alloys having a resistance to nitric acid comparable withl that oi' 10 kt. gold and suitable for replacing 10 and l2 kt. gold alloys in the jewelry art or the like are shown in the eld A-B-J-K Expressed in weight percentages, the composition of these `alloys may vary from about 15% to about.50% palladium, from about 45% to about 60% silver, and from about 5% to about 34% platinum. These alloys have in the annealed state a Rockwell B hardness of about 38 to about 75.

Those'alloys having a resistance to Vnitric acid comparable to 14 kt. gold and suitable as replacement alloys for 12 and 14 kt. gold alloys are shown in eld B-C-H-J, which comprises the alloys containing from about 21% to about 65% palladium, about 30% to about 45% silver, and about 5% to about 44% platinum. These alloys have a Rockwell B hardness, when annealed, of about 48 to about 80.

The alloysincluded in area C--D-G-H exhibit excellent resistance to nitric acid and tarnish and are suitable for the replacement of 14 and 18 kt. gold alloys. These alloys have in the annealed state a Rockwell B hardness of about 63 to about 90 and may contain from about 26% to about 82% palladium, about 13% to about 30% silver and about 5% to about 54% platinum.

Those alloys containing more than about 55% palladium plus platinum with a platinum content preferably of 9% or more possess excellent tarnish and nitric acid resistance, have high melting point and hardness, and are suitable for replacing gold alloys for jewelry, dental, electrical, and other uses where it is desirable to secure the aforementioned properties at a moderate cost. These alloys are included in area B-D-F-Q of the drawing.

When the total palladium plus platinum content is more than 55% and the platinum is preferably 15%'or more, the alloys possess extraordinary resistance to tarnish, to nitric acid, and increased resistance to hypochlorite antiseptics and have higher hardness and melting point. These alloys are indicated by the area B--D-E-N of the diagram and are most suitable ufor dental use where very severe conditions may be encountered.

As hereinabove more fully explained when the palladium content of the alloys is not less than about 60% of the platinum content thereof, the nobility of the alloy and especially its resistance to nitric acid is superior to that of gold alloys having a gold content equal to the palladium plus platinum content of the new alloy. T'he nobility of the alloys may further be increasedY by increasing the total palladium plus platinum content. For instance, alloys containing about 31 to 50% palladium, about 5 to 9% platinum and not morethan 60% silver, possess a higher resistance to nitric acid than the usual 10 kt. gold alloys.

from about 25% to about 46% and the silver content being not more than 60%, the resistance of the alloys to nitric acid is better than that of 12 kt. gold alloys. Ii the alloys contain 5v to 9% platinum, about 46 to 65% palladium and the silver is not in excess of 45%, the alloys show better resistance to nitric acid than 14 kt. gold alloys. Likewise, alloys containing 40% to 61% By raising the platinum content to about 9 to about 15%, the palladium content ranging palladium, about 9% to 15% platinum, the silver content being not more than 45% offer a resistance to nitric acid equal to that of 18 kt. gold alloys. t

`The hardness of the new alloys is largely dependent upon the combined percentages of the platinum alloy by the addition of a small percentage of copper, nickel and/or cobalt, for instance, in amounts varying from about 2% to about 10%. When the palladium plus platinum content of the alloys containing nickel or copper is not less than about 40% and the palladium content is not less than about 60% of the platinum content, the alloys not only possess increased hardness, but they are also substantially resistant to nitric acid. For instance, I found that alloys containing about 15% to about 82% palladium, about 5% to 54% platinum, about 413% to about 60% silver and about 2% to 10% copper or nickel, in which the palladium plus platinum content is 40% or more and the palladium is at least 60% of the platinum content, possess useful hardness and resistance to nitric acid. It should be noted that the amount of nickel must be restricted in alloys of high silver content to avoid the production of unhomogeneneous alloys which are less desirable where they are to constitute flat polished articles. Particularly useful alloys possessing high hardness and resistance to corrosion, especially nitric acid, may contain about 26% to 49% palladium, about 6% to 14% platinum, about 45 to 60% silver and about 2% to 10% nickel or copper. The corrosion resistance and hardness of the alloys containing nickel or copper may be improved by increasing the combined palladium plus platinum content thereof. When the total palladium plus platinum content is about 55% or more, I found that the alloy is not only hard and resistant to nitric acid, but is also substantially resistant to tarnish. Thus, I found that alloys possessing hardness, substantial resistance to nitric acid and superior resistance to atmospheric corrosion may contain about 41% to 64% palladium, about 6% to 14% platinum, about 30% to 45% silver and about 2% to 10% nickel or copper, the combined palladium plus platinum being not less than about 55%. When adding copper to the alloy, I found very surprisingly that the replacement of about 5% to 10% of the silver by an equal percentage of copper not only increases the hardness of the alloy, but also improves its resistance to nitric acid.

No difficulty is experienced in casting androlling the alloys if they are properly melted and are kept substantially free from oxygen, sulphur, tellurium, selenium or the like. Small amounts of deoxidizing and desulphurizing elements such as zinc, magnesium, manganese, silicon, boron, calcium, barium, titanium and zirconium may be utilized to improve the casting qualities of the alloys. Likewise, no difficulty is experienced in i casting the high melting point alloys suitable for dental uses if suitable equipment is used and proper care is exercised.

As an example, a particularly useful alloy having a resistance to nitric acid superior to 14 kt. gold alloys may be obtained by alloying 48.33% palladium, 10.00% platinum and 41.67% silver.

An alloy having a high melting point and excellent resistance to tarnish and corrosion may contain 60% palladium, 20% platinum and 20% silver.

The cost of the new palladium, platinum, silver alloys per unit of weight is less than that of a gold alloy containing an `amount of gold equal to the combined palladium plus platinum content of the new alloy, while their properties, especially resistance to tarnish and to nitric acid, are superior to those of the gold alloys. By virtue of the lower density of the new alloy, the cost per unit lNi-17.70 Ztl-6.00

Composition HNOa resistance Cost/oz. Cost/c.c.

PdP-Ag alloy (percent) Pri-48.33 .Pt-10 00 }Complete 14 kt. white gold alloy (percent) iu-58.33 Cu-l7.97

Good, but yellow $8. 36

stain results.

High-grade jewelry can be made fromthe solid alloy, but the less expensive grades can be made .from laminated stock, variously' called clad,

rolled, plated or lled stock, in which the outer surface may be composed of a layerof the new alloy welded or soldered to a, nickel or other suitable core. Composite material of this nature composed' of an outside surface layer of the new palladium, platinum, silver alloy and a core of a suitable base alloy has been manufactured successfully by methods similar to those employed in the production of gold filled wire. I have found that alloys containing about 26% to 64% palladium, about 6% to 14% platinum, and about 30% to 60% silver are especially suitable for cladding purposes.

It is tobe observed that the presentinvention provides a new white precious alloy containing palladium, platinum and silver whichis relatively inexpensive, easy to cast and to work, and

which has suilcient hardness, strength goodA wearing qualities and resistance to tarnish, corrosion and to nitric acid, as to be fully adapted for use in the production of jewelry or other purposes where high stability and moderate cost are essential.

vIt is further to be observed that by varying and controlling the proportion and/or ratios of the ingredients of the new palladium-platinumsilver alloys, as hereinabove more fully described, the alloy can have imparted thereto such a wide range of properties as to resistance to corrosion, hardness, strength, melting point, wearing qualities, etc., as to enable them to be adapted for a large and diversified number of uses and applications.

Furthermore, it is to be noted that the palladium-platinum-silver alloys provided by the present invention are not only less expensive, but are also superior inregard to resistance to tarnish and to nitric acid and other properties to known white gold alloys having a gold content substantially equal to the combined palladium plus platinum content of the new alloy.

Moreover, itis to be' noted that the invention provides a new white precious alloy of moderate cost and suitable for use in the jewelry and other arts, which contains substantially no gold, thereby offering an effective means for conserving gold and releasing it for essential monetary purposes.

Although the present invention has been described in conjunction with preferred embodiments, it is understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Thus, the alloy may be used for other purposes other than jewelry where high stability, high corrosion and erosion resistance, coupled with moderate cost, are essential, such as electrical, chemical, artistic applications and the like.

I claim:

1. An alloy, substantially resistant to nitric acid, consisting of to 82% palladium, 5% to 54% platinum, the palladium content always being at least 60% of the platinum content, and the balance consisting of silver, the said silver content being not less than 13% nor more than 60%.

2. An alloy, substantially resistant to nitric acid, consisting of 15% to 50% palladium, 5% to 34% platinum, the palladium content always being at least 60% of the platinum content, and the balance consisting of silver, the said silver content being not less than 45% nor more than 60%.

3. An alloy, substantially resistant to nitric acid, consisting of 21% to 65% palladium, 5% to 44% platinum, the palladium content always being at least 60% of the platinum content', l the balance consisting of silver, the said silver content being not less than nor more than 45%.

4. An alloy containing from to 70% of palladium and platinum of which 5 to 10% is platinum, the remainder of the alloy being silver.

5. An alloy consisting of about of palladium, about of silver and about 5% of platinum.

EDMUND M. WISE. 

